This invention relates generally to integrated circuits, and more particularly to controlling current demand in an integrated circuit.
Power supply voltage of a microprocessor, microcontroller, or any other type of integrated circuit or chip deteriorates with voltage undershoots and overshoots caused by changes in its power demand. Changes in power demand may occur when different instruction streams executed by an integrated circuit have different power demands, and in some situations, the change is drastic, such as when the integrated circuit comes out of or goes into a sleep state. This causes a problem in that the integrated circuit will malfunction if the power supply voltage varies beyond acceptable limits.
The large voltage variations during a drastic change of current are created mainly by the parasitic inductors in the package, bond wires, an on-chip interconnects. Therefore, the amount of overshoot or undershoot of the power supply voltage is directly proportional to dI/dtxc2x7{square root over (L/C)}, where L is the inductance of the package and on-chip interconnects and C is the integrated circuit (or on-chip) decoupling capacitance.
One solution to address this problem is to increase the integrated circuit decoupling capacitance such that the amount of voltage overshoot or undershoot is decreased. However, the feasibility of larger integrated circuit decoupling capacitors as a solution is limited due to the large area required within the integrated circuit to place these decoupling capacitors. Also, the effectiveness of any increased amount of decoupling capacitance is decreased since the amount of overshoot or undershoot of the power supply voltage is proportional to the square root of the increase of the decoupling capacitance. Furthermore, the problem of supply voltage overshoot and undershoot becomes increasingly worse as microprocessors, microcontrollers, or other integrated circuits become faster and current consumption is increased. Therefore, a need exists to monitor and control power supply voltage overshoots and undershoots in order to remain within acceptable limits.